WHAT A FLOWER IS 



175 



ing. It is very marked in ferns and mosses. In algae 

 (including the seaweeds) the gametophyte makes the 

 "plant," as the non-botanist knows 

 it. Then is a general tendency \ in 

 the evolution of th vegetable kingdom, 

 for tin gametophyte to lose its rela- 

 tivi importance and for tht sporophyte 

 to become larger dud more highly de- 

 veloped. In the seed-bearing plants 

 the sporophyte generation is the only 

 one seen by the non-botanist. The 

 gametophyte stage is of short dura- 

 tion and the parts are small: it is 



Confined to the time :;1 "- Fertile and sterile fronda 



c j> i.M j.- of the sensitive fern. 



ol fertilization. 



324. The sporophyte of seed-plants. 

 or the "plant" as we know it, produces 

 spores one kind being called pollen- 

 grains and the ether kind embryo-sacs. 

 The pollen-spores are borne in sporan- 



311. Asaclikeindusium. ^ whi( . h ..,. imi|( , a int() whft| ;m . 



ailed anthers. The embryo-sac, which contains the egg- 

 cell, is borne in a sporangium known as an ovule. A 

 gametophytic stage is presenl in 

 both pollen and embryo-sac : fer- 



I il i/.at inn takes place, and a sporo- 



phyte arises. Soon this sporo- 

 phyte becomes dormant, and is 

 t lien known as an < mbryo. The 

 embryo is packed awaj within 

 tight -lilt ing coats, and t he enl ire 



body is tin' seed. When tin- con- 

 ditions are right the Beed grows, 



and the sporophyte grow- into herb, bush, or tree. Tie 

 ntilii\ of the alternation of generations is not understood 



812. Prothallxu of ;i fi ra. En 

 Archegoo tntherldin at '. 



